The present invention is generally directed to layered photoresponsive devices, and imaging apparatus and processes thereof. More specifically, the present invention relates to an improved layered photoresponsive device comprised generally of a transport layer and a photogenerating layer. The layered photoresponsive devices of the present invention are useful as imaging members in various electrostatographic imaging systems, including those systems wherein electrostatic latent images are formed on the imaging member. Additionally, the photoresponsive devices of the present invention can be selectively irradiated with blue light, for example, as generated by a known blue diode laser, to accomplish, for example, latent image formation by, for example, charged area development (CAD) or discharge area development (DAD) methodologies.
Numerous photoresponsive devices for electrostatographic imaging systems are known including selenium, selenium alloys, such as arsenic selenium alloys; layered inorganic photoresponsive, and layered organic devices. Examples of layered organic photoresponsive devices include those containing a charge transporting layer and a charge generating layer. Thus, for example, an illustrative layered organic photoresponsive device can be comprised of a conductive substrate, overcoated with a charge generator layer, which in turn is overcoated with a charge transport layer, and an optional overcoat layer overcoated on the charge transport layer. In a further “inverted” variation of this device, the charge transporter layer can be overcoated with the photogenerator layer or charge generator layer. Examples of generator layers that can be employed in these devices include, for example, charge generator materials such as selenium, cadmium sulfide, vanadyl phthalocyanine, x-metal free phthalocyanine, benzimidazole perylent (BZP), hydroxygallium phthalocyanine (HOGaPc), and trigonal selenium dispersed in binder resin, while examples of transport layers include dispersions of various diamines, reference for example, U.S. Pat. No. 4,265,990, the disclosure of which is incorporated herein by reference in its entirety.
There continues to be a need for improved photoresponsive devices, and improved imaging systems utilizing such devices. Additionally, there continues to be a need for photoresponsive devices of varying sensitivity, which devices are economical to prepare and retain their properties over extended periods of time. Furthermore there continues to be a need for photoresponsive devices that permit both normal and reverse copying of black and white as well as full color images, especially in high speed digital printing systems.
In U.S. Pat. No. 4,410,616, to Griffiths, et al., issued Oct. 18, 1983, there is disclosed an improved ambi-polar photoresponsive device useful in imaging systems for the production of positive images, from either positive or negative originals, which device is comprised of: (a) supporting substrate, (b) a first photogenerating layer, (c) a charge transport layer, and (d) a second photogenerating layer, wherein the charge transport layer is comprised of a highly insulating organic resin having dissolved therein small molecules of an electrically active material of N,N′-diphenyl-N,N′-bis(“X substituted” phenyl)-[1,1,-biphenyl]-4,4′-diamine wherein X is selected from the group consisting of alkyl and halogen. There is also disclosed an example of a first photogenerator layer with a red light sensitive material such as a phthalocyanine, and a second photogenerator layer with a blue light sensitive material, such as amorphous selenium, wherein a red highlight color image can be obtained when the ambi-polar device is charged positively, see column 7, lines 28-39.
In U.S. Pat. No. 5,405,709, Apr. 11, 1995, Littman, et al., there is disclosed an internal junction organic electroluminescent device comprised of, in sequence, an anode, an organic electroluminescent medium, and a cathode, the organic electroluminescent medium further comprising a hole injecting and transporting zone contiguous with the anode and an electron injecting and transporting zone contiguous with the cathode, the electron injecting and transporting zone further comprising an electron injecting layer in contact with the cathode, characterized in that the portion of the organic electroluminescent medium that is interposed between the electron injecting layer and the hole injecting and transporting zone is capable of emitting white light in response to hole-electron recombination and comprises a fluorescent material and a mixed ligand aluminum chelate of the formula (Rs—Q)2—Al—O—L where Q in each occurrence represents a substituted 8-quinolinolato ligand, Rs represents an 8-quinolinolato ring substituent chosen to block sterically the attachment of more than two substituted 8-quinolinolato ligands to the aluminum atoms, O—L is a phenolato ligand, and L is a hydrocarbon group that includes a phenyl moiety. The compound 1,1-bis (di-4-tolylaminophenyl) cyclohexane (TAPC) is mentioned as a useful aromatic tertiary amine.
In U.S. Pat. No. 4,999,809, issued Mar. 12, 1991, Schildkraut, et al., there is disclosed a photorefractive device comprised of a first and second electrodes for establishing a potential gradient between first and second spaced locations and, interposed between the first and second electrodes, intermediate means capable of producing in a readout beam of electromagnetic radiation an image pattern corresponding to that present in a spatially intersecting writing beam of electromagnetic radiation when a potential gradient is applied to the intermediate means by said first and second electrodes. The intermediate means consists of a photorefractive layer capable of internally storing the image pattern of the writing beam created by its interference with an intersecting reference beam of electromagnetic radiation, the photorefractive layer being comprised of a homogeneous organic photoconductor containing organic noncentrosymmetric molecular dipoles capable of imparting to the photorefractive layer a second order polarization susceptibility of greater than 10−9 esu. The compound 1,1-bis (di-4-tolylaminophenyl) cyclohexane (TAPC) is also mentioned as a hole transporting agent, reference Example I.
In U.S. Pat. No. 5,876,887, issued Mar. 2, 1999, to Chambers, et al., there is disclosed an electrophotographic imaging member with a support, and at least one photoconductive layer having from about 90% by weight to about 10% by weight of the photoconductive particles of a photosensitive substituted perylene pigment, and, correspondingly, from about 10% by weight to about 90% by weight of at least one other n-type photosensitive pigment that is sensitive to shorter wavelength light than is the perylene pigment.
The aforementioned references are incorporated in their entirety by reference herein.
In the devices, imaging apparatuses, and processes of the prior art, various significant problems exist. For example, many conventional photoreceptor devices containing certain hole transport molecules (HTM) such as N,N′-diphenyl-N,N′-bis(3-methyl phenyl)-(1,1′-biphenyl)-4,4′-diamine (TPD) in an overlying charge transport layer cannot be successfully irradiated with specialized light sources, such as blue light generated from an aluminum-gallium-indium-nitride (AlGaInN) diode laser which source produces wavelength emissions, for example, of about 400 nanometers. This is because the certain hole transport molecules effectively absorb light at wavelengths below about 420 nanometers and thus prevent incident light from reaching the underlying charge generator layer. The application of a blue light diode laser irradiation source to electrophotographic imaging systems could potentially offer a number of significant and economic advantages, such as higher image resolution, improved print quality, and lower energy consumption. These and other advantages are enabled with the articles, apparatuses, and processes of the present invention.
There remains a need for articles, such as electroreceptors or photoreceptors, imaging apparatuses, and imaging processes which permits electrophotographic imaging systems to be efficiently and controllably irradiated with a blue light diode laser source.